Conventional sewage treatment plants use several different bacteria to break-down the waste and the ammonium and phosphates that are produced thereafter. Each of these bacteria needs different environments that must be created artificially. However, Gijs Kuenen at Delft University of Technology in theNetherlands has created a new process of cleaning sewage water that uses a recently discovered microorganism called anammox bacteria. It cuts out many of the bacteria normally needed, while producing methane as a byproduct, saving and giving energy at the same time.

One by-product of this [new] process is methane, which Kuenen proposes to harvest and use as fuel. The team calculates that, far from consuming energy, the process could generate 24 watt-hours per person per day. "This is about trying to make waste water treatment plants completely sustainable, in the sense that they could even produce energy, which is not the case in present treatment facilities," says Kuenen.